I just had the epiphany that the Liskov Substitution Principle may be generalised to category theory as a statement about co- and contravariance. A quick web search shows that @runarorama figured that out 10 years ago apocalisp.wordpress.com/2010…

Liskov Substitution Principle is Contravariance

The Liskov Substitution Principle is a much cited result by those who believe in the myth of “object-oriented programming”. But the LSP is like many things in the OO mythos that become …

apocalisp.wordpress.com
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Replying to @ploeh @runarorama
Don’t know about category theory, but surely the co/contravariance connection has been known even longer than that? I seem to recall the first time I read about the terms they were explained using LSP

Sep 29, 2020 · 1:21 PM UTC

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Replying to @stilkov @runarorama
You're probably right. FWIW, I increasingly feel disadvantaged by not having a formal CS education. I sometimes arrive at things like this from odd angles. I first read about LSP in one of @unclebobmartin's papers, and I don't recall if it discussed contravariance...
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I seem to recall covariant return types being introduced to C++ sometime in the late 90s, but I don’t recall the exact sequence of when I learned about what :)